I have an electric RC car. I need to replace the receiver antenna (it was nicked in a crash).
The Rx/Tx operate in FM at 26.995 MHz (crystal oscillator). The stock receiver antenna is 41 cm in length (which is somewhere between 1/32 and 1/16 wavelength). I was wondering if I should replace the antenna with something exactly at the 1/32 or 1/16 wavelengths (34.7 or 69.4 cm respectively).
So I did some searching and discovered that the antennae are not necessarily exact fractions of wavelength depending on the circuitry used by the receiver (the explanations of which were beyond my grasp).
Then I came across this site where a guy was able to determine some relationships between antennae length, configuration etc by measuring the voltage at an RSSI pin on his receiver chip:
RC-CAM Projects: R/C Antenna Experiments
I thought that it might be interesting (for me at least) to replicate some of the experiments because all he needed was a DVM and some knowledge of the FM demodulator IC (to find the RSSI pin).
So I found the datasheet for the chip that my car uses (MC3361BP) which can be found here:
https://www.utc-ic.com/spec/MC3361BP.pdf
But this chip does not have an RSSI pin.
So my question is whether it is possible to perform the same type of experiments on this chip (using only a DVM) and, if so, how?
As always - thanks in advance
p.s. I know I could just try different antenna lengths and drive the car until it fails to respond - I just thought the approach used in the link would be interesting to replicate.
The Rx/Tx operate in FM at 26.995 MHz (crystal oscillator). The stock receiver antenna is 41 cm in length (which is somewhere between 1/32 and 1/16 wavelength). I was wondering if I should replace the antenna with something exactly at the 1/32 or 1/16 wavelengths (34.7 or 69.4 cm respectively).
So I did some searching and discovered that the antennae are not necessarily exact fractions of wavelength depending on the circuitry used by the receiver (the explanations of which were beyond my grasp).
Then I came across this site where a guy was able to determine some relationships between antennae length, configuration etc by measuring the voltage at an RSSI pin on his receiver chip:
RC-CAM Projects: R/C Antenna Experiments
I thought that it might be interesting (for me at least) to replicate some of the experiments because all he needed was a DVM and some knowledge of the FM demodulator IC (to find the RSSI pin).
So I found the datasheet for the chip that my car uses (MC3361BP) which can be found here:
https://www.utc-ic.com/spec/MC3361BP.pdf
But this chip does not have an RSSI pin.
So my question is whether it is possible to perform the same type of experiments on this chip (using only a DVM) and, if so, how?
As always - thanks in advance
p.s. I know I could just try different antenna lengths and drive the car until it fails to respond - I just thought the approach used in the link would be interesting to replicate.